This invention relates generally to an open magnetic resonance imaging (MRI) magnet system, and more particularly to the support structures contained within the open magnet assembly.
Open MRI magnets are generally made with two magnetic pole pieces in the shape of thick disks. For a horizontal open magnet, the pole pieces are arranged with an upper horizontal pole and a lower horizontal pole. The imaging subject is inserted in the gap between the poles. Another arrangement has the planes of the pole pieces (often referred to as xe2x80x9cdouble donutxe2x80x9d) with the patient inserted through holes in the center of the pole pieces (the xe2x80x9cdonut holesxe2x80x9d). In this arrangement, a physician or other attendant can stand between the donuts and thereby have access to the patient.
Typically, there are strong magnetic forces between the pole pieces and, in the case of the horizontal magnet arrangement, the upper pole piece has considerable weight and must be supported. It is convenient to have strong and substantially stiff support posts between the pole pieces. It is desirable to have the posts confined to as narrow an angular region as possible to enhance the openness of the scanner. Narrow posts, however, are prone to vibration, which in turn affects imaging.
In higher field magnet systems, such as 0.7 Tesla (T) and above, vibration of support posts may be detected during imaging with a fast spin echo sequence. The effect is caused by the periodic application of imaging gradients that produce a resonance with the mechanical systems of the MRI system. As the support posts bend slightly, the magnetic field in the imaging volume is perturbed.
What is needed is a magnet arrangement for open MRI systems that reduces vibrations that affect imaging while maintaining the desirable openness of such systems.
In a first aspect, a magnet assembly system for use in an open Magnetic Resonance Imaging (MRI) system is provided and comprises a first assembly and a second assembly opposing each other in a longitudinally spaced apart relationship. The first and second assemblies generate a static magnetic field for use in imaging. Further provided is a plurality of support posts attached between the first and second assemblies for maintaining an open imaging volume between the first and second assemblies and for further providing structural support. Each of the support posts comprises a first support element and a second support element attached to first support element on the surface away from the imaging volume.
In a second aspect, a method for reducing vibration in an open MRI system is provided and comprises attaching a second support element to each of the support posts on a surface away from the imaging volume.